motivated by Fernando's problems I composed a little problem of my
own. It's not too difficult, your favorite chess engine will solve
it in a millisecond. So try it alone. The position is so simple that
it could have been done before though I do not know it. I hope you
will find it of practical value.

White to begin and draw:

White: Kf4, pa3
Black: Kd5, pb5

FEN: 8/8/8/1p1k4/5K2/P7/8/8 w - -

Solution below.

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It is obvious the white pawn is lost and White won't get the black
pawn in return. So White must go for a King vs. King and pawn endgame
where he can draw.

1. Ke3

The black pawn can´t be stopped without the king.

1...Kc4

The black king on his way to the white pawn. If now 2. Kd2
then 2...Kb3 will win for Black: 3. Kc1 Kxa3 4. Kb1 (4. Kc2 b4) Kb3
with a basic pawn endgame position or 3. a4 Kxa4 (not 3...bxa4 Kc1
and the white king either reaches the corner or locks in the black
king.) 4. Kc3 Ka3 5. Kc2 b4 6. Kb1 Kb3 again with the basic endgame
position.

2. a4!

The pawn is sacrificed so that Black's pawn is forced to the a-file.
If Black ignores the pawn then either both sides get a queen or the
Black king is forced behind his pawn.